Buttercup, the Yarn Eater

Hello, I have a 4 week old Buff Orpington chick, Buttercup, and she won't stop eating pink yarn. Even when I put it out of reach, she still gets into the bright pink yarn. The first time, she had only about 2 feet inside her and that didn't take long to extract. But the second time, she had consumed well over 5 feet of pink yarn. It took about 15 minutes for me to pull all of the yarn out of her. She is okay now, but she seemed a little frightened during the extraction. This pink yarn is not thick, but less than a 4 worsted yarn. What should I do if she does this again???

This same chick, my only chick or chicken, is best friends with my dog, a Rhodesian Ridgeback-Lab mix. We don't know why, but Buttercup is like my dog's own baby. She tries to play with it and my dog chases it around the yard, but does not bite Buttercup. She nudges her and licks her as if Buttercup were her own puppy. It's adorable! Any reasons WHY???